This invention relates to a method of soldering components or parts of a square chip or a mellophone type chip on a printed circuit board.
Heretofore, a soldering method includes a reflowing method and a dipping method. In these methods, the step of soldering components of chips is executed as below.
According to the reflowing method, a cream solder is applied by an automatic printing machine on predetermined portions of a printed circuit board, various types of predetermined chip components of necessary number are then placed in a fork-shape at the preliminarily soldering portions coated with the cream solder by an automatic charging machine, the entire board is contained in an automatic reflowing furnace while this state remains unchanged, the cream solder is melted by an infrared ray heating, air-cooled and solidified to simultaneously solder all the chip components by reflowing.
Therefore, the reflowing method should not only employ expensive facility cost for the automatic charging machine and the automatic reflowing furnace, but the chip components placed at the preliminarily soldering positions might be displaced by an external force such as a vibration with the result that the components might be soldered in an erroneously connected state. The work for correcting the displacement later becomes considerably complicated. Since the entire chip components are heated in the automatic reflowing furnace, a thermal adverse influence to the components arises as one of the drawbacks.
According to the dipping method, in means for soldering chip components known per se, cream solder is adhered in advance to predetermined positions on a printed circuit board, an adhesive is applied on the board, chip components to be soldered are bonded on the adhesive by an automatic charging-machine, the chip components are heated in a heating furnace to cure the adhesive, thereby soldering the adhering state of the components so that the state is held immovable, even if an external force such as a vibration occurs or the board is overturned upside down, the components are then heated at high temperatures by a soldering iron to melt the cream solder, the melted solder is then air-cooled and solidified.
According to the dipping method in this manner, various devices are required in addition to the reflowing method, expensive facility investments are not only required but the step of applying the adhesive is necessary in addition to the coating of the cream solder, and heating operation of curing the adhesive is required. Thus, considerable labor and time of soldering must be not only inefficiently consumed, but an expansion and contraction arise in a period to curing due to the heating and cooling steps of the adhesive. At this time the chip components might be removed from the designated positions so that the array of the chip components becomes irregular to reduce the vague of a product. Thus, there are drawbacks of having to check and correct the positions of the components.